1. Field
The present disclosure relates to positioning devices such as microscope stages. More particularly, the disclosure relates to a compact rotary flexure micropositioning stage with a large rotational range, and to a rotary stage which is based upon multiple-segment compound radial flexures.
2. Background
Micropositioning devices are widely employed to realize a precise positioning of the end-effectors dedicated to precision manipulation and assembly applications. Particularly, flexure-based compliant mechanisms have been extensively exploited due to their attractive merits in terms of no backlash, no friction, no wear, low cost, and vacuum compatibility. Unlike traditional mechanical joints, the repeatable output motion of a flexure mechanism is delivered by the elastic deformation of the material. Hence, the structural parameters of the flexure mechanism need to be carefully designed so that the material operates in the elastic domain without plastic deformation nor fracture failure.
A number of translational flexure micropositioning platforms have been reported in the literature and some of them have been commercialized on the market. In contrast, relatively limited works have been made toward the rotational micropositioning stage development. In the literature, some flexure stages providing combined translational and rotational motions have been reported. The present disclosure is focused on the design and development of rotary flexure stages which are capable of pure rotational motion. Several rotary flexure stages have been proposed previously; however, these stages are only able to deliver a small rotational angle less than 1°. In practice, many applications demand a rotary stage with a large rotational range. How to achieve a large rotational range by using flexure-based compliant mechanisms is a major challenge.
It is known that a flexure rotary stage can be devised using leaf flexures with fixed-fixed constraint. The rotational range of such devices is limited due to the over-constrained mechanism. To enlarge the rotational range, several rotary bearings have been presented and some rotary stages driven by smart material-based actuators (e.g., piezoelectric actuator and shape memory alloy) have been devised. Alternatively, the basic module of radial flexure can be employed to construct the compound radial flexures (CRFs). Yet, to achieve a large rotational range, the CRFs should be designed with a larger length, smaller thickness, and larger outer radius. Despite this, these physical parameters are restricted by the compactness requirement, manufacturing tolerance, and minimum stiffness requirement in practice. Thus, it is difficult to achieve a large rotational range while maintaining a compact stage size by using CRFs.